JP7210021B2 - Torque calibrating device and torque calibrating method for rotary torque transducer using electromagnetic force - Google Patents

Description

The present invention relates to a torque calibration device for a rotary torque transducer, and is used in fields such as precision equipment, measuring equipment, and medical equipment, where torque must be kept to a very small value and strictly controlled. The present invention relates to a torque calibration device and calibration method for calibrating a torque measuring device.

Conventionally, calibration (or testing) of torque measuring devices is generally performed by the gravity method by comparing with the torque generated by applying gravity to the tip of the lever.
Gravity method is an effective method that can achieve the most advanced torque at present. It has been adopted as a method to realize the national torque standard.

Patent Document 1 describes that when torque calibration is performed using torque generated by adding a weight to the tip of a lever, torque calibration is interrupted when long-period fluctuation occurs. there is
Non-Patent Document 1 describes a real-load torque standard machine developed by NMI in Germany that enables calibration of very small torques of 1 mN・m to 1 N・m. It is considered to be the torque standard machine with the highest accuracy for torque.

Japanese Patent Application Laid-Open No. 2001-133351

IPO science "Metrological characterization of a 1 N m torque standard machine at PTB, Germany" (posted by D. Roske on May 20, 2014)

For example, when manufacturing precision equipment and micro-equipment, the specified tightening torque value is extremely small, and strict maintenance and management are required.
However, in this gravitational method, there is a limit to manufacturing precision in reducing the mass of the weight to be loaded or shortening the length of the lever. Also, it is affected by gravity acceleration due to air flow and latitude difference. Non-Patent Document 1 describes that the actual load formula can be used to calibrate a torque value of 1 mN・m to 10 mN・m with an uncertainty of 0.1%, but the uncertainty is not sufficient for a torque standard machine. , It is very difficult to accurately calibrate minute torques of less than 1 mN・m using the actual load formula.

On the other hand, in the SI traceability system of torque currently proposed in Japan, the gravity type torque standard machine (actual load type torque standard machine) owned by NMIJ and the torque standard adopted by the first level calibration company It is necessary to compare between calibration devices, but due to the structure and weight of each device and the principle of torque generation, slight vibration affects accuracy, so the torque calibration device can be easily transported and relocated. I can't.
For this reason, we have no choice but to use an intermediary device (torque measuring device), and the results are inevitably greatly affected by the performance of the intermediary device used. A calibration method is required.

Therefore, in order to overcome such problems, the inventors proposed in Japanese Patent No. 6479605 to use torque generated by electromagnetic force instead of the conventional actual load formula, thereby achieving high precision even for minute torque. enabled calibration. As a result, the main body of the torque calibrator has been made more compact and easier to transport and install, making it possible to perform torque calibration (or testing) at the national standard level even at manufacturing sites.

In this torque calibration device, a torque transducer to be calibrated is connected to a coil installed in a magnetic circuit of opposite poles, and this coil is measured in advance against the torque generated when current is applied to this coil. (the angular position where the induced electromotive force V generated when the coil itself is rotated at a constant angular speed in the same magnetic circuit with opposite poles by a motor is the maximum value ) , the torque conversion to be calibrated The torque input to the device is specified with high accuracy. Therefore, the torque used for calibration was limited to static torque.
However, in order to calibrate rotary torque transducers with higher accuracy, it is necessary to calibrate them based not only on static torque that does not involve rotation, but also on rotational torque that is actually rotating. is.

Thus, it is impossible to calibrate a rotary torque transducer while rotating it, even with a conventional torque calibrating device composed of a calibration bar and a weight.
Also, for a rotary torque transducer capable of simultaneously measuring torque and number of rotations (rotational speed), torque and number of rotations (rotational speed) cannot be calibrated (or tested) at the same time.

Therefore, the object of the present invention is to make it possible to calibrate the torque and rotation speed (rotation speed) traceable to the International System of Units SI while rotating under conditions close to actual use conditions, and to improve the accuracy of the rotary torque transducer. It is to be realized.

A torque calibrating device for a rotary torque transducer according to the present invention comprises:
a magnetic circuit of opposite poles that forms a magnetic field with a magnetic flux density B;
a coil inserted inside the opposite pole facing type magnetic circuit;
a first rotary encoder;
a first servomotor coupled to one of the rotating shafts of the opposite poles facing type magnetic circuit via the first rotary encoder to rotate the different poles facing type magnetic circuit and keep it stationary at a specific angular position;
a second rotary encoder connected to the other of the rotating shafts of the coil;
a third rotary encoder;
a second servo motor;
The second rotary encoder and the input shaft of the rotary torque converter to be calibrated, one of the third rotary encoders and the output shaft of the rotary torque converter, and the other of the third rotary encoders and the second servo Couplings that connect the motors, respectively;
a control unit that controls the first servomotor and the second servomotor;
and a current control device for controlling the current I supplied to the coil.
Then, by driving the second servomotor while the first servomotor is mechanically locked and rotating the coil inside the opposite pole facing type magnetic circuit, the induced electromotive force V generated in the coil is Maximum value V _max angular position p ₀ Based on
With the first servomotor locked, current I is passed through the coil by the current control device, and the coil is driven against the torque generated in the coil based on the measurement results of the first and second rotary encoders. the angular position p ₀ controlling the second servo motor by the control unit so as to be stationary at
With the first servomotor unlocked, the coil moves to the angular position p based on the measurement results of the first and second rotary encoders. ₀ Synchronously rotating the first servo motor and the second servo motor by the control unit so as to maintain a stationary state at
With the first servomotor unlocked, the current I supplied to the coil is changed by the current control device, and the angular position p generated by the change in the current I is changed. ₀ Positioning control by the first servomotor or the second servomotor is performed by the control unit so that the deviation of the coil from the position is zero,
The rotational speed of the rotary torque converter is measured by the third rotary encoder while the first servomotor is unlocked.
Further, according to the present invention, a torque calibration method for a rotary torque transducer comprises:
A second servo motor is driven while mechanically locking a first servo motor connected to a magnetic circuit of opposite poles that forms a magnetic field of magnetic flux density B, and a coil is rotated inside the magnetic circuit of opposite poles. and the maximum value V of the induced electromotive force V generated in the coil _max and the induced electromotive force V reaches the maximum value V _max angular position p ₀ a step of identifying
A current I is applied to the coil while the first servomotor is locked, and the second servomotor rotates the coil and a rotary torque transducer to be calibrated that is connected to the coil. to move the coil to the angular position p ₀ and
With the first servomotor unlocked, the coil moves to the angular position p. ₀ performing synchronous rotation control of the first servomotor and the second servomotor so as to maintain a stationary state at
By changing the current I supplied to the coil, the angular position p caused by the change in the current I ₀ a step of performing positioning control by the first servomotor or the second servomotor so as to make the deviation from zero, and calibrating the rotary torque transducer;
measuring the rotational speed of the rotary torque transducer with the first servomotor unlocked;
including.

While rotating under conditions close to actual use, it will be possible to calibrate the torque and rotation speed (rotational speed) traceable to the International System of Units SI, and it will be possible to improve the accuracy of the rotary torque transducer.

FIG. 1 is a perspective view showing the force that a coil C receives from a magnetic field when a current I is passed through the coil C in a magnetic field with a magnetic flux density B. FIG. FIG. 2 is a view of the force that the coil C receives from the magnetic field when the current I is passed through the coil C in the magnetic field of the magnetic flux density B, viewed from the rotation axis direction. FIG. 3 is a perspective view showing the induced electromotive force generated when the coil C is rotated at the rotation angular velocity ω in the magnetic field of the magnetic flux density B. FIG. FIG. 4 is a view of the induced electromotive force generated after t seconds when the coil C is rotated at the rotation angular velocity ω in the magnetic field of the magnetic flux density B, viewed from the rotation axis direction. FIG. 5 shows the overall configuration of an embodiment of the present invention.

First, the basic principle of the present invention will be explained.
As shown in FIG. 1, a rectangular coil C (length L, height h, symmetrical with respect to the horizontal axis) that can rotate around the horizontal axis is placed in a vertically upward uniform magnetic field with a magnetic flux density B. When installed and a current I is passed through, the force F received from the magnetic field on the two sides perpendicular to the magnetic flux density is
F=I・B・L, or F=-I・B・L ........Equation (1)
becomes. That is, since the forces acting on the two sides perpendicular to the magnetic flux density are equal in magnitude and opposite in direction, a force couple occurs.

FIG. 2 shows a state in which the rectangular coil C is tilted by θ (hereinafter referred to as "angular position") with respect to the direction of the magnetic lines of force. At this time, the torque T acting on the coil C is
T=I・B・L・h・cos θ=I・B・A・cos θ Expression (2)
It can be expressed as.
Here, A = L · h, that is, when A is the area of the coil and the coil C has N turns,
T=N・I・B・A・cos θ ・・・・・・・・・・・・ Formula (3)
becomes.
From the equation (3), the maximum value (absolute value) _Tmax of the torque T is |cos θ| 2, 3, etc.),
T _max =N・A・B・I ・・・・・・・・・・・・・・・・ Equation (4)
becomes.

In order to achieve torque with high accuracy, it is required to set or measure each parameter on the right side of Equation (4) with high accuracy.
Although the angular position θ and the current I can be measured with relatively high accuracy, it is extremely difficult to measure the shape of the coil C (the number of turns N and the area A) and the magnetic flux density B with high accuracy.
Therefore, in order to offset the magnetic flux density B, the area A of the coil C, and the number of turns N, as shown in FIG. The induced electromotive force V generated in is measured in advance.
That is, by rotating the coil C at a constant rotational angular velocity ω (π/s) by the motor M in a magnetic field with the same magnetic flux density B as when generating torque, an induced electromotive force V is generated in the coil C. .
Assuming that the normal vector of the coil C coincides with the direction of the magnetic force line as the origin (t=0), as shown in FIG. The induced electromotive force V is
V=N・A・B・ω・sinωt ・・・・・・・・・・・・ Equation (5)
is represented by

Here, the maximum value (absolute value) V _max of the induced electromotive force V is sinωt =1, and ωt=− (n+1/2)π (n=0 , 1, 2, 3...),
V _max =N・A・B・ω・・・・・・・・・・・・・・・・ Equation (6)
becomes.
As described above, this is the same angular position as when the current I is passed through the coil C in the magnetic field of the magnetic flux density B and the generated torque reaches the maximum value _Tmax .
Therefore, in advance, the coil C is rotated at various rotation speeds ω _i by the motor M in the magnetic flux density B, and the maximum induced electromotive force V _{max_i} and the angular position p _{0_i} of the coil C at that time are calculated for each rotation speed as Record.
Taking ω _i on the horizontal axis and V _{max_i} on the vertical axis, N·A·B, which is the inclination thereof, is obtained by an approximation formula.
Note that the average value of p _{0_i} is p _0/ .

Next, while the coil is held at the angular position p _{0 /} by the motor M, a current I is passed through the coil C. As shown in FIG.
At this time, by equation (4),
T _max /I=N・A・B ・・・・・・・・・・・・・・・・ Equation (7)
Then, according to formula (6),
V _max /ω=N・A・B ・・・・・・・・・・・・・・・・ Equation (8)
Furthermore, from equations (7) and (8),
_Tmax ·ω= _Vmax ·I Expression (9)
becomes.

Equation (9) shows that the mechanical power and the electrical power are equal, N, A, B are all eliminated, V _max (voltage value), I (current value), ω (rotational angular velocity ), and the positioning accuracy of the coil C makes it possible to increase the accuracy of T _max to the level of the current highest performance actual load type torque standard machine described in Non-Patent Document 1.

Specifically, in the present invention, in advance, the coil C is rotated by the motor M at the rotational angular velocity ω _i in the magnetic field of the magnetic flux density B, and the maximum value V _{max_i} of the generated induced electromotive force and the angular position p at that time Measure and record _{0_i} repeatedly.
By repeating the above measurements and recordings while varying the rotational angular velocity ω _i , the relationship between ω _i and V _{max_i} is obtained, and the slope thereof is calculated by the method of least squares or the like to obtain the following equation (6): , the magnetic flux density B and the shape of the coil C (number of turns N and area A) can be evaluated. Strictly speaking, the angular position of V _max should not change at any rotational angular velocity, and the measurement results of p _{0_i} are considered to have a normal distribution _{. Let 0/} be the angular position where the induced electromotive force is maximum.

Next, in the magnetic field of the same magnetic flux density B, the angular position of the coil C is held at the average value p _{0 /} by the motor M, and the current I is passed through the coil C,
T _max =I·V _max /ω ・・・・・・・・・・・・・・・・・・・・Equation (10)
becomes.
That is, T _max can be specified by measuring the pre-evaluated V _max /ω (equipment-specific constant) and the current I, and by inputting this torque to the calibrated object can be calibrated.

Based on this basic principle, embodiments of the present invention will be described below.
FIG. 5 shows the overall configuration of this embodiment.
The output shaft of the first servomotor (1) is connected to a magnetic circuit (4) having opposite poles through a first coupling (2a) and a first rotary encoder (3).
On the other hand, the output shaft of the second servomotor (9) is connected to a rotary torque transducer to be calibrated via a fourth coupling (2d), a third rotary encoder (8) and a third coupling (2c). It is connected to the input shaft of (7).
In addition, the output shaft of the rotary torque transducer (7) to be calibrated is arranged in the opposite pole facing type magnetic circuit (4) via the second coupling (2b) and the second rotary encoder (6). connected to the coil (5).

With the above configuration, the rotation angle of the output shaft of the first servomotor (1), that is, the rotation angle of the opposite pole facing type magnetic circuit (4) is determined by the first rotary encoder (3) and the coil (5). is measured by a second rotary encoder (6). Furthermore, the rotation angle of the rotary torque transducer (7) is measured by a third rotary encoder (8). The measured values of the first rotary encoder (3) and the second rotary encoder (6) are input to a program controller PLC (10) which includes a motor synchronization control unit. In addition, in order to improve the measurement accuracy, a self-calibrating rotary encoder is used as the third rotary encoder (8), and although the counter and terminal block (14) are illustrated, depending on the required accuracy , a normal rotary encoder may be employed in the same manner as the first rotary encoder and the second rotary encoder.

The coil (5) is supplied with current from a precision variable current source (source measure unit) (12) via a slip ring (11).
The first servomotor (1) and the second servomotor (9) are connected to SSCNET II/III and MECHATROLINK-II/III via servo amplifiers, respectively, for precise synchronous control and high-speed operation between multiple servomotors. It is connected to a program controller PLC (10), which constitutes a control unit, via a network with emphasis placed on it, and its rotation speed and output torque are individually controlled.

In the figure, (13) is an indicator for the rotary torque transducer, (14) is a counter and terminal block for the self-calibrating rotary encoder (8), and (15) is a PC that analyzes and displays the measurement results. .

When calibrating the rotary torque transducer (7), first, as proposed in Japanese Patent No. 6479605, the output shaft of the second servo motor (9) is connected to the fourth coupling (2d) and the third coupling (2d). Rotary encoder (8), third coupling (2c), rotary torque transducer (7), second coupling (2b) , connected to rectangular coil (5) via second rotary encoder (6). to rotate. As a result, the parameters of the opposite pole facing type magnetic circuit (4) and the rectangular coil (5) arranged inside it, that is, the magnetic flux (B) set in the different pole facing type magnetic circuit (4) The total magnetic flux (NAB) passing through a rectangular coil (5) of area A and number of turns N is evaluated.
Specifically, the induced electromotive force V generated when the rectangular coil (5) is rotated at the angular velocity ω by the second servomotor (9) is measured, and V (V=NABω) becomes the maximum value _Vmax . Measure the angular position p ₀ of the rectangular coil (5) at the time. At this time, the output shaft of the first servomotor (1) is mechanically locked by an electromagnetic brake or the like so that the magnetic circuit (4) facing opposite poles does not rotate.

With the rotary torque transducer (7) mounted between the second coupling (2b) and the third coupling (2c), the opposite poles opposed type magnetic circuit (4) is applied to the rectangular coil (5). Positioning control is performed by the second servo motor (9) so that the angular position p ₀ is reached, and the difference between the first rotary encoder (3) and the second rotary encoder (6) is reduced to zero when the angular position becomes p ₀ . reset to
In this state, when a current I is supplied from the precision variable current source (12) to the rectangular coil (5) through the slip ring (11), a torque is generated on the measurement axis indicated by the dashed line in the figure, and the rectangular coil (5) is twisted by Δp.
The angular position deviation is measured (taken the difference) from the first rotary encoder (3) and the second rotary encoder (6), and the first rotary encoder (3) and the second rotary encoder (6) are rotated by using the second servo motor (9). The rotary encoder (6) is controlled so that the difference is zero. At this time, the torque generated on the measurement axis indicated by the dashed line is strictly defined by T=NAB·I (Tω=VI), and this torque T is applied to the rotary torque transducer (7).

In this state, the first servomotor (1) is unlocked, and the program controller PLC (10) is used to perform synchronous control of the first servomotor (1) and the second servomotor (9). The transducer (7) is rotated under a load of T, which is strictly defined as above.
At the same time, the third rotary encoder (self-calibrating rotary encoder ) ( 8) evaluates the change in angular position (rotation speed) per unit time. The first rotary encoder (3 ) and the second rotary encoder (6) to be zero, various torque values can be calibrated.

According to this embodiment, the current can be changed continuously instead of discrete changes in torque as in the case of the test bar and the weight. Even if the positions of the first rotary encoder (3) and the second rotary encoder (6) are shifted by changing the current I, the first rotary encoder (3) and the second rotary encoder (6) By evaluating the angular difference, the strictly defined torque (T=NAB·I) can be corrected by a trigonometric function.
For the bearings of each component, when the highest level is required as a torque calibrating device, it is preferable to use air bearings instead of ordinary ball bearings in order to reduce the influence of friction.

The torque calibration device according to the present embodiment comprises a different pole facing type magnetic circuit that forms a magnetic field with a magnetic flux density B, a coil inserted inside the different pole facing type magnetic circuit, and a first rotary encoder. A first servomotor connected to one of the rotating shafts of the pole-opposed magnetic circuit to rotate the opposite pole-opposed magnetic circuit and keep it stationary at a specific angular position; A rotary encoder, a second rotary encoder and an input shaft of a rotary torque converter to be calibrated, one of the third rotary encoder and an output shaft of the rotary torque converter, and the other of the third rotary encoder and a second servo motor a voltage measuring unit that measures the induced electromotive force V generated in the coil, a control unit that controls the first and second servo motors, and a current I supplied to the coil A maximum value V of the induced electromotive force V measured by the voltage measurement unit when the second servo motor rotates the coil at the rotation angular velocity ω with the opposite pole facing type magnetic circuit locked. _max and the angular position p ₀ , the coil is moved to the angular position p ₀ The torque input to the torque converter is controlled by controlling the second servomotor so that the second servomotor is kept stationary at the angle position p ₀ Synchronously rotate the first servomotor and the second servomotor so as to maintain a stationary state, and the current control device so that the difference between the rotation angles measured by the first rotary encoder and the second rotary encoder becomes zero. While changing the current I supplied to the coil, the rotation speed based on the change per unit time of the rotation angle measured by the third rotary encoder, and the load applied to the rotary torque transducer in the rotating state The torque value is evaluated at the same time.
If a rotary torque converter can be made highly accurate, it will be useful in promoting the development of engines and motors, which are objects of evaluation for rotary torque converters, such as higher accuracy and energy saving.
In particular, according to this embodiment, the following effects can be achieved as compared with the conventional real load type calibration device.
(1) A torque load can be applied to the rotary torque transducer while rotating it.
(2) Torque and speed can be calibrated (or tested) simultaneously for rotary torque transducers.
(3) Dynamic evaluation is possible for rotary torque transducers.
(4) A minute torque can be reproduced with high accuracy.
(5) It becomes possible to reduce weight, size, and cost.
(6) Evaluation of gravitational acceleration according to latitude is unnecessary.
(7) It is less likely to be mechanically damaged during transportation, and even if it is damaged, it is easy to re-evaluate after transportation (the magnetic flux density of the magnetic circuit and the shape of the coil).
(8) Therefore, the primary standard of torque can be easily realized even at a manufacturing site or the like.
(9) By building a new torque SI traceability system, it is possible to promote the development of new torque measuring devices.

As described above, according to the present invention, regardless of the shape of the coil or the density of the magnetic field generated by the magnetic circuit of the opposite pole facing type, by passing a current through the coil in the magnetic field, even a minute torque can be reproduced with high accuracy. It is possible to calibrate (or test) the torque and number of rotations (rotational speed) while the torque transducer is actually rotating, so it can be widely adopted as a more accurate torque calibration device. I can expect it.

1: 1st servo motor 2a-2d: 1st-4th couplings 3: 1st rotary encoder 4: Opposite magnetic circuit 5: Coil 6: 2nd rotary encoder 7: Rotary torque transducer 8 : Third rotary encoder 9: Second servo motor 10: Program controller PLC
11: slip ring
12: precision variable current source
13: Indicator for rotary torque transducer
14: counter and terminal block
15: PC

Claims (4)

a magnetic circuit of opposite poles that forms a magnetic field with a magnetic flux density B;
a coil inserted inside the opposite pole facing type magnetic circuit;
a first rotary encoder;
a first servomotor coupled to one of the rotating shafts of the opposite poles facing type magnetic circuit via the first rotary encoder to rotate the different poles facing type magnetic circuit and keep it stationary at a specific angular position;
a second rotary encoder connected to the other of the rotating shafts of the coil ;
a third rotary encoder;
a second servo motor;
The input shaft of the second rotary encoder and the rotary torque converter to be calibrated, one of the third rotary encoders and the output shaft of the rotary torque converter, and the other of the third rotary encoders and the couplings respectively connecting the second servo motors ;
a control unit that controls the first servomotor and the second servomotor;
A current control device that controls the current I supplied to the coil,
The induced electromotive force V generated in the coil is maximized by driving the second servomotor while the first servomotor is mechanically locked and rotating the coil in the opposite pole facing type magnetic circuit. Based on the angular position p ₀ at which V _max is
With the first servomotor locked, current I is passed through the coil by the current control device , and the coil is driven against the torque generated in the coil based on the measurement results of the first and second rotary encoders. controlling the second servomotor by the control unit to rest at the angular position _p0 ;
With the first servomotor unlocked, the coil is maintained stationary at the angular position _p0 based on the measurement results of the first and second rotary encoders. Synchronously rotating the second servo motor by the control unit ;
With the first servomotor unlocked, the current I supplied to the coil is changed by the current control device, and the displacement of the coil from the angular position p0 caused by the change in the current I is reduced to zero _. Positioning control by the first servomotor or the second servomotor is performed by the control unit so as to
The rotation speed of the rotary torque converter is measured by the third rotary encoder while the lock of the first servomotor is released.
Torque calibration device for rotary torque transducers. Said first servomotor and said second servomotor are each connected to said control unit via a servo amplifier, and the rotational speed and output torque thereof are individually controlled. A torque calibration device for a rotary torque transducer according to item 1. 3. A torque calibrating device for a rotary torque transducer according to claim 1, wherein a self-calibrating rotary encoder is used as said third rotary encoder. A second servo motor is driven while mechanically locking a first servo motor connected to a magnetic circuit of opposite poles that forms a magnetic field of magnetic flux density B, and a coil is rotated inside the magnetic circuit of opposite poles. and specifying the maximum value V _max of the induced electromotive force V generated in the coil and the angular position p ₀ at which the induced electromotive force V becomes the maximum value V _max ;
A current I is applied to the coil while the first servomotor is locked, and the second servomotor rotates the coil and a rotary torque transducer to be calibrated that is connected to the coil. resting the coil at the angular position _p0 against the torque developed ;
performing synchronous rotation control of the first servomotor and the second servomotor so that the coil remains stationary at the angular position _p0 with the first servomotor unlocked ;
Positioning control is performed by the first servomotor or the second servomotor by changing the electric current I supplied to the coil so as to make the deviation from the angular position p0 caused by the change of the electric current I _zero . and calibrating the rotary torque transducer ;
measuring the rotational speed of the rotary torque transducer with the first servomotor unlocked;
A torque calibration method for a rotary torque transducer comprising :

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